Bladder type accumulator with core tube



Jan. 28, 1969 KAZUO SUGIMURA ET AL. 3,424,201

BLADDER TYPE ACCUMULATORWITH CORE TUBE Filed June 13, 1966 United States Patent 40/ 56,530 US. Cl. 138-30 4 Claims Int. Cl. F16] 55/04 ABSTRACT OF THE DISCLOSURE A bladder type of accumulator with a central core having; longitudinal fins to promote a regular shape during inflation and deflation, flaps covering the core communicating holes to protect the bladder, and a poppet valve at the lower end of the core tube.

This invention relates to the improvement of accumulators of pressure liquid type, consisting of a cylindrical and rigid pressure liquid tank, and of an elastic and flexible cylindrical gas bag, generally called a bladder, filled with gas under a certain standard pressure, and equipped 'within the liquid tank.

The important features of the bladder are that it inflates and deflates regularly in a certain designed manner, and that it does not collapse into irregular shapes both crosswise and longitudinally.

Most of the bladders of conventional accumulators are of plane wall, and when deflated, are collapsed at random into irregular shapes in cross section, and then are bent longitudinally.

Thus the bladder wrinkles and crumples, which causes sharp folds in its flexible wall, which is spoiled, torn and ruptured. Useful life of the bladder is thus much shortened. The random collapsing of bladders not only shortens their useful lives, but also reduces their shock absorbing capacity.

T o avoid the defect of random collapsing, some of the improved bladders have longitudinal reinforcements in their cylindrical Wall, so that the bladders deflates regularly to pre-designed forms in the cross section.

Although a few bladders of this device succeeded to a certain extent, but strictly speaking, resistance against longitudinal bending is not suflicient when the bladders are extremely deflated.

In the conventional bladder type accumulator, the liquid port is generally closed by the bladder by pushing the poppet valve down against its valve seat, equipped at the gate of liquid port. The flexible wall of bladder, which thus directly contacts With and pushes the valve, is easily spoiled by the sharp edge and corner of the valve, and by the projection of valve arrangement. Moreover, the flexible wall of bladder is often caught and pinched by and between the valve and its seat. Useful life of the bladder is thus again much shortened. This is also another defect of the conventional.

Here, we have to mention another defect of the conventional accumulator, in which the valve mechanism, to close or open the oil port of liquid tank, is equipped within the liquid port along its centre line, and offers resistance to the liquid agaianst its free flow through the port. Thus, the important feature to absorb hydraulic shocks is much reduced.

The present invention eliminates all these defects of conventional accumulators, and offers a sensible shock absorbing apparatus characterized by constant, steady, and ample accumulating capacity over its long entire lifetime.

FIG. 1 is the longitudinal section and FIG. 2 is the cross section of the accumulator, while FIG. 3' represents the 3,424,201 Patented Jan. 28, 1969 cross section of the bladder how its cross section changes in the source of deflation.

The liquid tank 1 is of a cylindrical shape and is tapered conically at the ends, to make openings 2 and 3 for gas and liquid respectively.

The gas bag 5 is also of a cylindrical shape and tapered conically towards the ends, one of which is opened and flanged as shown by 6, and is tightly fastened to the liquid tank at its opening 2 by a gas valve housing 10 and a nut 11.

A gas valve :12 is equipped on the gas valve housing 10 to charge the gas bag 5 with gas to a certain standard pressure. The gas valve may be replaced by a pipe 13 to connect the gas bag to a certain pressure gas source. In this case, the accumulator is called a transfer barrier to transfer fluid. At the other end of the gas bag 5, a poppet valve 9 is tightly and integrally equipped to compose the bottom of the gas bag, so that the valve faces its valve seat 4, which is equipped at the other opening end of the liquid tank to form a liquid port 3.

A core tube 7 is installed'within the gas bag 5 by being rigidly fixed to the gas valve housing 10 at the upper end. At the lower end of the core tube 7, a valve guide 14 is rigidly equipped to serve as a seat for the fully opened poppet valve 9 and to slidably support and guide the valve by its valve spindle 15. A coil spring 17 is provided between the valve guide 14 and a spring seat 16, which is fixed at the end of the valve spindle 15 to push the poppet valve upwards to open. A suitable number of longitudinal fins 8 of elastic and flexible material are radially fixed to the core tube 7 along its outer surface, to give resistance against the wall of deflating gas bag 5.

The core tube fitted with flexible longitudinal fins may easily be inserted into the bladder and the liquid tank through the flanged end and the opening 2 respectively, with fins bent as shown by chain line 8' in FIG. 2.

Through the wall of the core tube 7, a suitable number of small communicating holes 18 are perforated so that gas can flow freely to follow the change of the volume of the gas bag.

When an accumulator as above described is installed to a pressure liquid system and connected with its pressure pipe through the liquid port 3 pressure liquid will enter the liquid tank 1 through the liquid port, so long as the pressure of pump delivery or of the pressure circuit is higher than that of the gas within the gas bag 5. The gas pressure in the gas bag, always balancing to that of the liquid in the liquid tank 1, the gas bag deflects to accumulate pressure liquid into the liquid tank from, and reversely inflates to discharge pressure liquid out of the liquid tank to the pressure circuit.

The important features for the gas bag is, as already mentioned, that the gas bag inflates and deflates smoothly and regularly in a certain designed manner, and that when it deflates, it does not collapse into irregular shapes both in crosswise and longitudinal directions, as to be described later.

As long as the flexible wall of the gas bag of cylindrical form works under tension, the bag keeps its natural cylindrical shape, but in the course that the bag is compressed and deflated, as soon as the tension within the wall becomes zero (when the tension becomes zero, it will hereinafter be defined that the wall is at its inflection point), the cylindrical wall of the bag of uniform thickness begins to deform at random to an iregular shape in cross section, which is the defective feature of conventional accumulators, as already mentioned.

In the present invention, the gas bag is so made that the cylindrical wall is at its inflection point when the inner surface touches the tips of the longitudinal radial fins 8, as shown in the FIG. 2b. Therefore, when the gas bag has come to this condition in the course of deflation, the

gas bag begins to collapse at random. But due to the resistance oflFered by the longitudinal radial fins 8 against deflation, the gas bag 5 cannot deflate at random, but deflates as shown in FIG. 3c. When the gas bag further deflates, it will take the form as shown in the FIG. 3d, and further it will deflate to the extreme, so that the cylindrical wall touches the whole surface of fins 8 as well as the surface of core tube 7 as shown in the FIG. 3e, and this extremely deflated form is the pre-designed regular form of extreme deflation of the gas bag 5. A flap 19 with a vent may be provided on the outer surface of core tube 7 over each communicating hole 18, so that the wall of extremely deflated gas bag may not protrude into the hole 18.

Thus, the gas bag 5 never fails to deflate regularly to the pro-designed form in its cross section as shown in the FIG. 3's, and thus supported by the core tube 7, the deflated gas bag is always kept straight without being bent longitudinally.

Thus, the major defects to shorten the useful life and decrease the accumulating capacity as well as the shock absorbing capacity of the conventional accumulator caused by the random collapsing of gas bag are eliminated.

As the liquid circuit pressure drops, the accumulated liquid begins to be discharged out of the liquid tank 1 through the port 3, and the deflated gas bag will inflate radially in the reverse way as shown in the FIG. 3s, until its cylindrical wall touches the cylindrical wall of liquid tank, and then the gas bag will inflate longitudinally towards the liquid port 3, until at last the poppet valve 9 which is integrally equipped to the gas bag at its bottom, will, being guided by the valve guide 14 and compressing the valve spring 17, approach is valve seat 4, and at last, will touch the seat to close the liquid port 3. A full course of inflation from extreme deflation of the gas bag or of pressure liquid discharge is thus completed.

A course of deflation of gas bag or of liquid accumulation into the liquid tank will be completed just reversely as above described.

In the course of inflation as well as deflation of the gas bag, due to the construction of the gas bag, equipped with the poppet valve 9 and due to the arrangement and mechanism of this valve and its seat 4, the flexible wall of the gas bag never touches the valve seat. Therefore, there is no chance for the wall to touch the sharp edge or corner of the valve and its seat or no chance to be caught and pinched by and between the valve seat to be spoiled and to shorten its useful life.

Here it is to be mentioned that as the poppet valve mechanism, instead of being installed within the liquid port as in the conventional accumulator, is installed completely within the gas bag as shown in the FIG. 1, there is no obstacle in the liquid flow through the liquid port 3. Therefore, liquid can flow into or out of the liquid tank freely without being interrupted.

This is why the accumulator of this invention is very sensible against the pressure change and absorbs hydraulic shocks much better than the conventional.

Here is another point of advantage claimed for this accumulator. In the conventional accumulator, owing to the buoyancy of the gas bag is bent longitudinally when it is deflated as already described and even in its inflated state, the gas bag, being supported at one end and owing to its flexible material, is bent, like a loaded cantilever, when the accumulator is installed inclined or horizontally, and therefore, its flexible wall rubs against the wall of oil tank which causes wear and tear to the flexible wall and sensibility of absorbing shocks of the gas bag.

While in this invented accumulator, the gas bag is, being supported and kept always straight along the centre line of the liquid tank by the core tube 7, and therefore, it is clear that the defect of the conventional accumulator as above mentioned are all eliminated.

We claim:

1. A bladder type accumulator comprising a cylindrical liquid tank made of rigid material and a cylindrical gas bag made of flexible and elastic material concentrically disposed within said tank, the outer diameter of said gas bag being smaller than that of said liquid tank, said liquid tank being provided with a gas inlet at one end and a valve seat at the other end, said gas bag being secured at one end to the gas inlet end of said liquid tank while the other lower end of said gas bag is free;

a core tube of rigid material disposed within said gas bag one end of which is secured to the gas inlet end of said liquid tank and the other lower end of which terminates adjacent the free lower end of said gas bag, said core tube having a plurality of longitudinal disposed fins radially extending therefrom a distance corresponding to the inflection point of the elastic gas bag, said core tube defining a plurality of small communicating holes therethrough, a flap with a vent on said core tube for each of said communicating holes;

poppet valve means at the lower end of said gas bag including a valve guide at the lower end of said core tube disposed within said gas bag, a valve spindle guided slidably within said valve guide, a valve member carried by said valve spindle integral with and closing the free end of said gas bag, and spring means along said spindle to bias said valve member away from said valve seat.

2. A device in accordance with claim 1 wherein said valve member is generally flat, said spring is a coil spring, said valve guide is rigidly attached to the bottom of said core tube and forms at its bottom a second valve seat for said generally flat member in which said spring normally biases said flat valve member, and said spindle is provided at its upper end with a seat for said spring.

3. A device in accordance with claim 2 wherein said fins are formed of flexible and elastic material.

4. A device in accordance with claim 2 further comprising a gas valve at said gas inlet.

References Cited UNITED STATES PATENTS 2,342,356 2/1944 Mercier 138-30 3,115,162 12/1963 Posh 138-30 3,138,176 6/1964 Mercier 13830 3,143,144 8/1964 Peet 13830 3,182,685 5/1965 Mercier 13830 3,319,420 5/1967 Mercier 138--30 XR 3,364,949 1/1968 Sugimura 13830 LAVERNE D. GEIGER, Primary Examiner.

BRADFORD KILE, Assistant Examiner. 

